hello all, as the title says, I have swapped my transmission with one with 67,000 miles. However, after swapping it, the car goes into limp mode, and a transmission fault Error appears. My mechanic says that it is a transmission programming issue, that he will have to fix, but that doesn't make any sense, because the original programmed transmission ecu was also installed with the transmission. Does anybody have any ideas?

 

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There is NO NEED to replace a fully functional TCM on the AJ26/AJ27 ZF5HP24.(the correct software is already loaded in the TCM)

The TCM with the SAME VCATS /xxx suffix with work with ANY similar gearbox.

Put your original TCM in the CAN bus and see if that fixes your issue.

There might actually be an issue with the replacement gearbox to cause the gearbox fault?

What DTC(s) is/are logged in the TCM?

 

Thats the thing, the original TCM of the replacement was loaded in as well. Man I really hope its not an actual gearbox issue. As for DTC's, I'm not sure, the mechanic said it said something about programming on there but I'm not sure that's even thing. Do you mean to put the original 100k TCM from the old gearbox on the replacement?

 

BOTH TCMs should have the same VCATS.

 

[QUOTE=ericnunez;2700095]Thats the thing, the original TCM of the replacement was loaded in as well. Man I really hope its not an actual gearbox issue. As for DTC's, I'm not sure, the mechanic said it said something about programming on there but I'm not sure that's even thing. Do you mean to put the original 100k TCM from the old gearbox on the replacement?[/QUOTE

Yes, motorcarman said put your original TCM back in. There was no need to change it.

 

[QUOTE=RJ237;2700233]I was told by the "Jag Specialist" who sold me the replacement to swap in the new TCM with the replacement, as using the old TCM could result in issues. So that's what I did.

 

So then its almost certainly a gearbox issue?

 

motorcarman probably knows a lot more than your 'specialist'.

 

He does, I'm just stating why I had the TCM replaced along with the trans.

 

Okay, so, according to my mechanic, he now tried using the trans with both TCMs, and both TCMs resulted with the same problem. Limp mode and transmission fault dash code. He says the issue is actually being caused by something electrical, and, according to him, it's because the engine and transmission are not communicating properly. He says he's trying to find where the issue is. My question is, is that possible? Or is it certainly a gearbox issue?
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Realized I posted this reply twice. (Thanks slow internet)

 

Have them check:

1) The main electrical connector on the back of the transmission should be clean and dry. Check for any damaged or folded over pins.

2) The electrical connector on the top side of the transmission for the range switch should be plugged in and hopefully all pins are making proper contact and none of the wires are pinched between the engine and transmission.

3) The ground cable going from the transmission to the body on the passenger side in front of the catalytic convertor should have a good clean connection.

4) Have them record the codes from the ECM and TCM and please post them on here. I’m sure it’s already been done but, I’d advise to clear the codes with the key on, engine OFF, do not try to start it, disconnect the scanner, perform hard reset then try to retest everything again.

5) If all else fails, maybe a wiring issue inside the replacement transmission??

 

Will do, thanks for the response.

 

Alright, so I wasn't able to get the codes as my mechanic gave the car to an electrician, with whom I have no contact with. However, the electrician was able to verify that the transmission wiring was all clean and undamaged. According to him it's the PCM that is not communicating with the transmission. I find this weird as the check engine light is not on, and OBD doesn't find any errors. The mechanic supposedly found a replacement PCM and will try to replace it tomorrow.

 

Hmmm, that’s a new one to me. Anyways, unless they have a proper machine to have the replacement ECM to shake hands with the KTM, it’s not going to start. The ecm’s are not plug n play.

 

Sorry, not to sound like an idiot, whats the "KTM"?

 

Key Transponder Module. There’s a chip inside the key and when you stick it in the ignition switch, the outside circumference of the switch has an antenna. The programmed key is recognized by the KTM and sends an ok to start to the ECM.

 

A replacement ECM needs an IMMOBILIZATION SETUP.

Once the setup is complete you cannot install the original ECM without ANOTHER 'immo-setup' to configure to original back to the CAN bus.(THERE CAN BE ONLY ONE)

You can install the replacement ECM and then try to start the engine only to find out you need an 'immo-setup' then realize you don't have the equipment so the original can be reinstalled and everything is back the way it was.

 

According to my mechanic, the electrician told him that its the ECM not communicating so more than likely it will have to be replaced. He also states that he has someone who will be able to program the ECM for the car. So the replacement should work.

 

Very interesting, the mechanic says he has a guy that will be able to program it. Do you think maybe just part of the ECM is damaged? And not the whole ECM? If I remember correctly, a car won't even start with a bad ECM.